Super-resolution “nanoscopes” can dramatically increase the resolving power of light microscopes, revealing novel details of organelle structure, function and dynamics in living cells. Nevertheless, the complex requirements for nanoscopy pose real challenges for both fluorophore design and labelling logic. The fluorophore must be bright, photostable and live cell-compatible, and the labelling method must yield a high fluorophore density that is benign to organelle function. As nanoscopes push the resolution envelope to tens of nanometers, there is a critical need for high density probes that demark organelle boundaries with sufficient photostability to study organelle dynamics.
While most nanoscopy applications rely on labelled proteins, lipids represent a complementary attractive target, as they are present at approximately a hundred-fold higher density and their organization defines the de facto boundary of the organelle. Commercially available fluorescent lipids, such as BODIPY® FL C5-ceramide, are cell permeable and have been used widely to label the Golgi, but they bleach too rapidly for prolonged imaging or super-resolution methods. Photostable dyes typically used for STED microscopy, such as commercially available ATTO® 647N and STAR635, suffer respectively from non-specific 1779117.1 binding and lack of cell permeability, and are ill suited for live cell STED microscopy of intracellular structures such as the Golgi.
There is a need in the art to identify novel compositions, and methods using same, that may be used for imaging intracellular structures. Such compositions should be cell permeable and allow for live cell microscopy of intracellular structures. The present invention addresses and meets this need.